Identification media in the form of plastic cards often contain a magnetic strip which is magnetized with numeral values used in connection with personal identification. These values are combined with a personal code in a procedure for verifying that card and person are complementary. Such a procedure is described in the U.S. Pat. No. 4,214,230. However, the magnetic information on the magnetic strip can rather easily be changed by erasion and writing in new information. This may result in that a criminal organization can duplicate and manufacture such cards themselves.
So-called "secure cards" have been devloped and are now on the market, the term implying that the card contains permanent information which was put into it when it was produced, and this information can not be altered or put into a card produced by others not originally producing it, since this would require access to original production apparatus. At present this permanent number is used in connection with personal identification number (PIN) verification, such that the number is compared with a range of numbers allowable for the card number and if the permanent number is within this range, the check is considered to be approved.